The information raises fresh questions about how closely the Trump campaign vetted staff members and whether Manafort and Gates told officials about their interactions with the FBI.
Jason Maloni, a spokesman for Manafort, declined to comment, citing a gag order imposed by the judge in Manafort’s case.
A lawyer for Gates did not immediately respond to requests for comment, nor did Michael Glassner, executive director of Trump’s campaign committee.
Manafort resigned as Trump’s campaign chairman in August 2016 after a series of stories were published about his work in Ukraine, including a New York Times report that alleged he had received more than $12 million in off-the-books payments from Viktor Yanukovych’s political party.
Manafort denied receiving the payments and doing anything improper in Ukraine but said at the time that he was stepping down to spare the campaign distraction.
In all, three Trump associates are known to have been interviewed by the FBI about their interactions with people from the former Soviet Union before joining the Trump campaign.
The FBI also interviewed campaign foreign policy adviser Carter Page about his interactions with a man the FBI alleged was a Russian intelligence agent. The interviews occurred in 2013 and in March 2016 — the same month Page was named a volunteer adviser to Trump’s campaign.
Page has said that he did nothing wrong and that he assisted the FBI in its investigation of a New York-based Russian spy ring.
A person familiar with Manafort’s work on the campaign said there was no information to suggest that the FBI had alerted the campaign to any concerns the bureau had with Manafort.
The new court filings indicate that prosecutors provided Manafort with copies of his past interviews to help him prepare for trial on charges including conspiracy, money laundering, and tax and bank fraud. Manafort has pleaded not guilty.
Gates pleaded guilty to conspiracy and lying to the FBI in February and is cooperating with Mueller’s investigation.
Manafort worked as a political consultant in the former Soviet state beginning in 2005, ultimately helping to elect Yanukovych president in 2010. Yanukovych was ousted after public protests in 2014 and fled to Moscow.
Manafort’s work in Ukraine had been the subject of news reports and was known before he joined the campaign, but his FBI interactions were not publicly known beforehand.
In a previous court document, Manafort said he met voluntarily with the FBI and prosecutors with the Justice Department in July 2014 to discuss his “offshore consulting activities.” BuzzFeed reported in February that Manafort had been interviewed in 2014 as part of an investigation of Yanukovych’s spending.
The newly filed documents show that Manafort also gave statements to the FBI during the investigation last year, including after his condominium in Alexandria, Va., was searched in July and after he was arrested in October.
The documents were filed as Manafort fights in court to have evidence that was seized from a Virginia storage unit excluded from use at his trial.
He also has sought to have the charges against him dismissed, saying that Mueller’s office exceeded its authority by charging him with crimes that do not relate to Russian meddling in the 2016 campaign.
Manafort is scheduled to go to trial in Virginia in July and on related charges in Washington in September.
Tom Hamburger and Spencer S. Hsu contributed to this report.